You can either find them in certain caves or just buy them at Pokemon marts in the "advanced" places (where there are stronger leveled Pokemon)
You can probaly catch him with a ultra ball but I would use the master ball
Put it to sleep then use an ultra ball.
yes u can, that's whut i did and now i have a moltres
No, you do not need a master ball, if you get it to a low enough hp, you can catch it with an ultra ball. You can find mew in the end of the cave in cerulean.
To catch an articuno with an ultra ball you have to lower it's HP and put it to sleep... To catch a moltres you only have to lower his HP then use an ultra ball... To catch a zapdos a master ball is required... Or you could get a gameshark!
Go to the pokemart in cinnabar island and there they sell them. Also at the elite four theres a lady to the right side she sells stuff she also sells ultra balls
You cannot turn an Ultra Ball into a Master Ball.
In a shop
The ultra ball for sure
you cant make a master ball with an ultra ball
For Zapdos: Go through the power plant and use your master ball, If Master ball has been used then attempt to capture with Great ball or Ultra ball. For Moltres: Go to Mt. Ember and climb to the summit and Moltres will be waiting. Use your Master ball, If used try to capture with Great ball or Ultra ball. For Articuno: Go to the Sea foam caves and move the boulders through the empty holes ( Strenght HM Is needed ) Articuno is tricky to catch. Use your Master ball, If used try to capture with Great ball or Ultra ball.
you have to use ultra balls